Shields attribute requirement seems to scale with its tier when dropped/bought.
T1: 10
T4: 19
T7: 32
T9: 42
So once I start dropping T5+ shields, they become unusable on hybrid character which might have 26 or so in two damage scaling attributes.
But if I take T1 shield and start upgrading it, it will always have 10 attribute requirement. There is workaround to create new realm or hoard shields early, but it is inconsistent and inconvenient.